Oliver Reichenstein:

Promising to make you look wired and magically promote your content in social networks, the Like, Retweet, and +1 buttons occupy a good spot on pretty much every page of the World Wide Web. Because of this, almost every major site and world brand is providing free advertising for Twitter and Facebook. But do these buttons work? It’s hard to say. What we know for sure is that these magic buttons promote their own brands — and that they tend to make you look a little desperate. Not too desperate, just a little bit.